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IC 


8894 



Bureau of Mines Information Circular/1982 



How To Evaluate Longwall Dust Sources 
With Gravimetric Personal Samplers 



By Steven J. Page, Robert A. Jankowski, 
and Fred N. Kissell 




UNITED STATES DEPARTMENT OF THE INTERIOR 



Lpformation Circular 8894 

How To Evaluate Longwall Dust Sources 
With Gravimetric Personal Samplers 



By Steven J. Page, Robert A. Jankowski, 
and Fred N. Kissell 




UNITED STATES DEPARTMENT OF THE INTERIOR 
James G. Watt, Secretary 

BUREAU OF MINES 
Robert C. Horton, Director 




This publication has been cataloged as follows: 



A 



h 






O^ 



©' 



Page, Steven J 
















How to evaluate 


longwall c 


I U.St sources 


with 


gravimetric 


personal j 


samplers. 
















( Bureau of Mines 


information 


circular ; 8894). 










Includes bibliographical refe 


rences. 












Supt. of Docs, no 


.: I 28.27:8894. 












]. ( oal mines and mining— 


Dust control 


. 2. 


Mine (. 


lusts- 


M 


?asure- 


mcnt. 1. Jankowsk 


, Robert A 


» II. Kisse 


11, Frt 


d N. 


III. 1 


it 


e. IV. 


Series; Information 


circular (IJ 


nited States 


Bureau of 


Mines 


) 


. 8894. 


TN^^&im 622s |622'.42l 


fTN312] 


82-600229 









CONTENTS 

Page 

Abstract 1 

Introduction 2 

Sampling method 2 

Sampling strategy 2 

Calculation examples of mine data 5 

Mine 1 — unidirectional head-to-tall cutting sequence with support movement 

of shearer Intake 6 

Mine 2 — unidirectional tall-to-head cutting sequence with support movement 

on shearer Intake 7 

Mine 3 — bidirectional cutting sequence 8 

Mine 4 — unidirectional tall-to-head cutting sequence with support movement 

on shearer return 9 

Mine 5 — unidirectional head-to-tall cutting sequence with support movement 

on shearer Intake 10 

Summary 11 

Appendix A. — Sampling sequence 12 

Appendix B. — Shearer operator dust source contributions for shearers in 

coiiq>llance 13 

Appendix C. — Filter weights and error considerations 14 

ILLUSTRATIONS 

1 . Hand-held sampler packages 3 

2. Sampler vest... 4 

3. Sampling location designations 5 

TABLES 

1. Dust source data for mine 1 6 

2. Dust source data for mine 2 7 

3. Dust source data for mine 3. 8 

4. Dust source data for mine 4 9 

3. Dust source data for mine 5 10 

B-1, Typical longwall double-drum shearer dust source contributions obtained 

from a survey of six longwalls regularly in compliance.... 13 



i 



HOW TO EVALUATE LONGWALL DUST SOURCES 
WITH GRAVIMETRIC PERSONAL SAMPLERS 



By Steven J. Page, 1 Robert A. Jankowski,2 
and Fred N. Kissel! 3 



ABSTRACT 

Longwall double-drum shearers frequently have difficulty complying 
with the 2,0 mg/m^ dust standard and, therefore, require the use of 
effective dust controls. However, before dust controls can be imple- 
mented effectively, the major individual dust sources must be determined 
and their relative severity evaluated. 

The Bureau of Mines has recently developed a sampling strategy, based 
upon short-term gravimetric sampling, that can identify the major dust 
sources contributing to the shearer operator's exposure. This technique 
utilizes approved gravimetric sampling equipment already available to 
all mine operators and can be performed by two people in 2 days. Five 
examples, including data analysis, are discussed with respect to various 
cutting sequences. 

In addition, typical dust source contributions obtained from studies 
of double-drum shearer operations regularly in conqjliance are included. 
Mine operators can thereby con5)are their dust source evaluation results 
with those from these longwalls. 

'Physicist. 
^Physical scientist. 
■'Supervisory physical scientist. 

All authors are with the Pittsburgh Research Center, Bureau of Mines, Pittsburgh, 
Pa. 



INTRODUCTION 



The objective of this report is to pro- 
vide to the mine operator a sampling 
strategy for evaluating longwall dust 
sources and the range within which the 
dust concentrations for these sources 
should lie. This is important because 
major dust sources must be identified be- 
fore dust controls can be recommended and 
applied correctly. The shearer operator 
is typically a high-risk, occupation; for 
this reason the sampling strategy pre- 
sented is aimed at the shearer operator's 
exposure to the major dust sources. 

The standard method of evaluating dust 
exposure is by collecting personal sam- 
ples over an 8-hr period. Although this 



method is the most appropriate estimate 
of a worker's full-shift exposure, it is 
far from adequate for identifying dust 
sources and their severity or for evalu- 
ating the effectiveness of dust control 
techniques. The Bureau has recently 
developed an uncon5)licated sampling 
strategy, based upon short-term gravi- 
metric sampling, that works effectively. 
This technique utilizes approved gravi- 
metric sampling equipment already avail- 
able to all mine operators. The objec- 
tive is not to precisely define the dust 
source contributions, but to allow the 
mine operator to determine suffioiently 
where dust problems are in the shortest 
and simplest way. 



SAMPLING METHOD 



Evaluating longwall dust sources re- 
quires that two kinds of dust samples 
be taken: (1) stationary and (2) 
mobile. It is necessary for both kinds 
that a minimum of four personal samplers 
be used. Multiple samplers arranged 
in a package are necessary to insure 
accuracy and to obtain a valid average 
measurement of the respirable dust con- 
centration because sampling is done for 
short periods of time (typically 20 to 
30 min).4 

For stationary samples, figure 1 shows 
two recommended methods, as it is 



important to keep the cyclone samplers 
within a 12-inch radius. 

For mobile samples, two techniques are 
available. Either a package can be hand- 
carried, as shown in figure 1, or the 
sampler vest, shown in figure 2, can be 
used. The sampler vest is simply a fish- 
ing vest that contains four large pockets 
suitable for holding the sampling pumps; 
the four cyclone samples are located on 
the right and left lapels of the vest. 
This particular arrangement gives the 
wearer hand freedom to make other mea- 
surements, such as airflow. 



SAMPLING STRATEGY 



It is important to note that the sam- 
pling strategy is based upon the fact 
that the dust concentration measured at 
any location is a composite of all dust 
sources upstream of that location. The 

■^In general, all four of the measured 
dust concentrations in each package 
should be used for determining the aver- 
age concentration. However, you should 
use your own judgment in omitting one of 
the values from the calculation if ( 1 ) 
one of the values is substantially dif- 
ferent or (2) a sampler was known not to 
be functioning properly during the test. 



sampling locations, designated in fig- 
ure 3, are the same, regardless of cut- 
ting sequence; they allow the mine oper- 
ator to determine the shearer operator's 
exposure to the major dust sources: 

A — section intake 

B — 15 ft on shearer intake, tail-to-head 

C — midpoint of shearer, tail-to-head 

D — 15 ft on shearer intake, head-to-tail 

E — midpoint of shearer, head-to-tail. 





FIGURE 1. = Hand-held sampler packages. 




FIGURE 2. = Sampler vest. 



I 



Headgate 



a 



, 



o 



\ 



n 




KEY 

Section intake, stationary 

15 ft on shearer intal(e, tail to head pass only, mobile 

Midpoint of shearer, tail to head pass only, mobile 

15 ft on shearer intake, head to tail pass only, mobile 

Midpoint of shearer, head to tail pass only, mobile 

Direction of shearer-sampler movement 

Face ventilation 



Stage loader 



i^^M^ 



15 ft 1 



IZZ 



■ - I r-1 .1 , ,K^ 
Shearer |>ji^;:}; 



D 



SUTv^vT^^LC^ 



T 



C- 



Roof support line 

FIGURE 3. - Sampling location designations. 



The sampling strategy is carried out by 
a survey team consisting of two individu- 
als, with each collecting the mobile 
gravimetric samples during selected seg- 
ments of the mining cycle. The sampling 
is divided into two main phases: 

1. A set of samples collected on the 
head- to- tail pass. 5 



2, A different set of samples 
lected on the tail-to-head pass. 



col- 



One individual stands at the midpoint of 
the shearer, and the other stands approx- 
imately 15 to 20 ft on the intake air 
side of the shearer. In addition, there 
is a stationary sampler package, located 
in the last open crosscut, to measure the 
section's intake dust concentration. 
Appendix A provides a s tep-by-s tep sam- 
pling sequence as an example. 



CALCULATION EXAMPLES OF MINE DATA 



In the following examples, the sampling 
locations are those designated in fig- 
ure 3. At the top of each table pre- 
sented are the sampling locations and 
sampling times, as well as the dust con- 
centrations obtained at each location. 

^A pass is defined as movement from 
either head-to-tail or tail-to-head. 



The dust concentration and sampling 
times at the various locations are 
average values for all passes. These 
average values are then treated as if 
they were obtained on one single pass. 
In the lower portion of the table are 
listed the dust sources and the calcula- 
tion of their contributions. For exam- 
ple, the section intake contribution is 



simply the value of A; the stage loader- 
conveyor contribution is obtained by sub- 
tracting A from B and is designated (B- 
A), and so forth for the other dust 
sources. The time fraction of the mining 
cycle is simply the percentage of the 
total sampling time for both passes that 
a given dust source contributes to the 
shearer operator's exposure. 

avg source contribution (mg/m^) = dus 

X t 

Appendix B is provided to allow the 
mine operator to conqjare the provided 
examples, as well as sampling results 
from the mine, with the shearer operator 
dust source contributions for shearers in 
compliance. 

Appendix C provides information on 
filter weight requirements and sampling 
error considerations. 

Mine 1 — Unidirectional Head-to-Tail 
Cutting Sequence With Support 
Movement on Shearer Intake 

Mine 1 has roof support movement on the 
intake air side of the shearer during the 
head-to-tail cut. 



For all examples, the ventilation in- 
take is at the headgate, and there are no 
atypical operations that affect the sam- 
pling results. 



The average 
(tables 1-5) is 
equation 



source contribution 
obtained from the 



t source concentration (mg/m^) 

ime fraction of mining cycle (pet). 

Results of the sampling analysis are 
shown in table 1. According to table 1, 
the section intake (A) contributes 1 pet 
to the total source contribution 100 pet 
of the time; the stage loader-conveyor 
(B-A), operating 100 pet of the time, 
contributes 23 pet to the total; roof 
support movement (D-B),6 operating 67 pet 
of the time, contributes 11 pet to the 
total; the head-to-tail shearer cut (E- 
D), operating 67 pet of the time, eon- 
tributes 62 pet to the total; and the 
tail-to-head shearer cleanup (C-B), oper- 
ating 33 pet of the time, contributes 
3 pet to the total. 



TABLE 1. - Dust source data for mine 1 



Sampling location^ 


A 


B (cleanup) 


C (cleanup) 


D (cut) 


E (cut) 


S amn 1 i n p t imp ......... mi n . . 


42 
0.1 


14 
1.8 


14 
2.3 


28 
3.0 


28 


Dust concentration. .mg/m3, , 


9.9 


Dust source 


A 


B-A 


D-B 


E-D 


C-B 


Descriotion. •...•...•••••.. 


Section 
intake. 

0.1 
100 
0.1 

1 


Stage 
loader- 
conveyor. 

1.7 

100 

1.7 

23 


Support 
movement. 

1.2 

67 
0.8 

11 


Shearer 
(cut). 

6.9 

67 
4.6 

62 


Shearer 


Dust source concentration 

mg/m3, , 
Time fraction of mining 

cycle pet. . 

Average source contribution 

mg/m3. , 
Percent of total 
source contribution^ 


(cleanup). 

0.5 

33 

0.2 

3 



^See figure 3. 

^Total source contribution, 7.4 mg/m3; this represents average exposure during cut- 
ting and not exposure for conqjliance purposes. 



^Calculation of the roof support movement contribution (D-B) is based on the 
assumption that the stage loader-conveyor contribution is the same on both cleanup 
and cutting. Table 4 indicates that there is no significant difference, although 
this may not always be true. 



This mine was regularly out of compli- 
ance. The short-term sampling has iden- 
tified two problem areas: (1) the head- 
to-tail cut (62 pet); and (2) the stage 
loader-conveyor (23 pet). Referring to 
table B-1 (appendix B), both of these 
values lie outside the ranges for the 
cleanest longwalls. Efforts can now be 
concentrated on these two areas to 
achieve compliance. For this operation, 
the shearer cut the full seam on the 
head-to-tail pass. The effect of this 
cutting sequence placed the trailing 
headgate drum (which is cutting bottom 
coal) on the intake air 
shearer. A logical 
would be to employ a 
tional head-to-tail 
where the bottom coal is cut on the tail- 
to-head cleanup by the tailgate drum. 
This has the effect of putting the bottom 
cut on the return air side of the shearer 
rather than on the intake air side. 



side of the 
corrective measure 
modified unidirec- 
cutting sequence7 



Mine 2 — Unidirectional Tail-To-Head 
Cutting Sequence With Support 
Movement on Shearer Intake 



Mine 2 has roof support movement on the 
intake air side of the shearer during the 
head-to-tail cleanup pass. 

Results of the sampling analysis are 
shown in table 2. According to table 2, 
the section intake (A) contributes 13 pet 
to the total source contribution 100 pet 
of the time; the stage loader-conveyor 
(B-A), operating 100 pet of the time, 
contributes 7 pet to the total; roof sup- 
port movement (D-B), operating 36 pet of 
the time, contributes 7 pet to the total; 
the tail-to-head shearer cut (C-B), oper- 
ating 64 pet of the time, contributes 
20 pet to the total; and the head-to-tail 
shearer cleanup (E-D) , operating 36 pet 
of the time, contributes 54 pet to the 
total. 



TABLE 2. - Dust source data for Mine 2 



Sampling location^ 


A 


B (cut) 


C (cut) 


D (cleanup) 


E (cleanup) 


Samolincr time. •.•••••• .mln. • 


55 
0.6 


35 
0.9 


35 
2.3 


20 
1.6 


20 


Dust concentration. . .mg/m^. . 


8.5 


Dust source 


A 


B-A 


D-B 


C-B 


E-D 


Description 

Dust source concentration 

mg/m3. . 
Time fraction of mining 
cvele. ..••....••••••• .net. • 


Section 
intake. 

0.6 

100 

0.6 

13 


Stage 
loader- 
conveyor. 

0.3 

100 

0.3 

7 


Support 
movement. 

0.7 

36 

0.3 

7 


Shearer 
(cut). 

1.4 
64 

0.9 
20 


Shearer 
(cleanup) . 

6.9 
36 


Average source contribution 

mg/m3. . 
Percent of total 
source contribution^ 


2.5 

54 



^See figure 3. 

^Total source contribution, 4.6 mg/m^; this represents average exposure during cut- 
ting and not exposure for con5)liance purposes. 



'U.S. Bureau of Mines. Modifieci Cutting Sequence Reduces Longwall Shearer Oper- 
ators' Dust Exposure. Technol. News, No. 116, 1981. 



8 



This mine was regularly in conqjliance. 
However, notice that the head-to-tail 
cleanup, which was only a third of the 
mining cycle, contributed more than one- 
half of the shearer operator's dust ex- 
posure. The reason for this is that, on 
the cleanup pass, the headgate drum was 
cutting bottom rock on the intake air 
side of the shearer. It is well known 
that cutting rock creates a much larger 
amount of dust. Similar to that for mine 
1, a corrective measure would be to use a 
modified unidirectional tail-to-head cut 
where the entire seam is cut on the tail- 
to-head pass. This would place the bot- 
tom cut (rock grinding) on the return air 
side of the shearer. 

Mine 3 — Bidirectional Cutting Sequence 



tail-to-head cut and on the intake air 
side of the shearer during the head- 
to-tail cut. 

Results of the sampling analysis are 
shown in table 3. According to table 3, 
the section intake (A) contributes 43 pet 
to the total source contribution 100 pet 
of the time; the stage loader-conveyor 
(B-A) , operating 100 pet of the time, 
contributes 19 pet to the total; the roof 
support movement (D-B), operating 55 pet 
of the time, contributes 7 pet to the 
total; the tail-to-head shearer cut (C- 
B), operating 45 pet of the time, con- 
tributes 31 pet to the total; and the 
head-to-tail shearer cut (E-D) , operating 
55 pet of the time, contributes pet to 
the total. 



Mine 3 has roof support movement on the 
return air side of the shearer during the 



TABLE 3. - Dust source data for Mine 3 



Sampling location-^ 


A 


B (cut) 


C (cut) 


D (cut) 


E (cut) 


Samolinc time •••••••••••••• .min. • 


47 
1.8 


21 
2.6 


21 
5.5 


26 
3.2 


26 


Dust concentration mg/m^. . 


3.1 


Dust source 


A 


B-A 


D-B 


C-B 


E-D 


Descriotion. ••••••••••••••••••.•• 


Section 
intake. 

1.8 

100 

1.8 

43 


Stage 
loader- 
conveyor. 

0.8 

100 

0.8 

19 


Support 
movement. 

0.6 

55 
0.3 

7 


Shearer 
(cut). 

2.9 

45 
1.3 

31 


Shearer 


Dust source concentration 

mg/m3. . 
Time fraction of mining cycle 

pet, . 
Average source contribution 

mg/m3. . 
Percent of total source 
contribution^ 


(cut). 

20.0 

55 







is actually negative: see section "Mine 3" and Appendix C for 



^See figure 3. 

^Quantity (E-D) 
explanation. 

^Total source contribution, 4.2 mg/m^; this represents average exposure during cut- 
ting and not exposure for con^jliance purposes. 



Notice that, although roof support 
movement occurs on both passes, that is, 
100 pet of the time, only 55 pet of the 
time is attributed to it. The reason for 
this is that the shearer operators are 
exposed to roof support dust only on the 
head-to-tail cut. The roof supports are 
moved on the return air side of the 
shearer during the tail-to-head cut, and, 
thus, do not contribute. 



Another apparently strange result is 
the 0-pct contribution (see appendix C) 
of the shearer on the head-to-tail cut. 
Inspection of the quantity (E-D) shows 
that it is actually slightly negative. 
This says that since the sample 15 ft on 
the shearer intake air side is slightly 
greater than the value at the shearer 
midpoint, the dust at the shearer mid- 
point is essentially a combination of 



only coal transport dust and roof support 
movement dust. This physically makes 
sense because on the head-to-tail pass, 
the tailgate drum is cutting most of the 
coal (and making the most dust) and is on 
the return air side of the shearer. The 
headgate drum is on the shearer intake 
air side but is cutting very little coal 
and, therefore, making very little dust. 

This mine was regularly out of compli- 
ance. Inspection of the results shows 
where the problem area is: the section 
intake (43 pet). 

Mine 4 — Unidirectional Tail-to-Head 
Cutting Sequence With Support 
Movement on Shearer Return 

Mine 4 has roof support movement 
on the return air side of the 



shearer during 
pass. 



the 



tail-to-head cut 



Results of the sampling analysis are 
shown in table 4. According to table 4, 
the section intake (A) contributes 15 pet 
to the total source contribution 100 pet 
of the time; the stage loader-conveyor on 
the cut pass (B-A), operating 71 pet of 
the time, contributes 10 pet to the to- 
tal; the stage loader-conveyor on the 
cleanup (D-A) , operating 29 pet of the 
time, contributes 8 pet to the total; the 
tail-to-head shearer cut (C-B), operat- 
ing 71 pet of the time, contributes 
63 pet to the total; and the head-to-tail 
shearer cleanup (E-D), operating 29 pet 
of the time, contributes 5 pet to the 
total. 



TABLE 4. - Dust source data for Mine 4 



Sampling location 1 


A 


B (cut) 


C (cut) 


D (cleanup) 


E (cleanup) 


Sampling time .......... .min. . 


51 
0.6 


36 
1.2 


36 

4.7 


15 
1.6 


15 


Dust concentration. .. .mg/m3. . 


2.2 


Dust source 


A 


B-A 


D-A 


C-B 


E-D 


Description. ................. 


Section 
intake. 

0.6 

100 

0.6 

15 


Stage 
loader- 
conveyor 
(cut). 

0.6 

71 
0.4 

10 


Stage 
loader- 
conveyor 
(cleanup) . 

1.0 

29 

0.3 

8 


Shearer 
(cut). 

3.5 
71 

2.5 
63 


SViPP fPT" 


Dust source concentration 

mg/m3. . 
Time fraction of mining 

cycle pet. . 

Average source contribution 

mg/m3. . 
Percent of total source 
contribution^ 


(cleanup) . 

0.6 

29 

0.2 

5 



^See figure 3. 

^Total source contribution, 4.0 mg/m^; this represents average exposure during cut- 
ting and not exposure for con5)lianee purposes. 



Since the support movement is on the 
return air side of the shearer, it does 
not contribute to the shearer operator's 
exposure and is, therefore, not being 
measured. However, although there is no 
roof support dust measurement, there is 
an additional stage loader-conveyor dust 
measurement. 



Although the majority of the dust 
(63 pet) is from the headgate drum (in- 
take air side of shearer) on the tail- 
to-head cut, this mine was regularly in 
co^^)liance. 



10 



Mine 5 — Unidirectional Head-to-Tail 
Cutting Sequence With Support 
Movement on Shearer Intake 



Mine 5 has roof support movement on the 
intake air side of the shearer during the 
head-to-tail cut. 

Results of the sampling analysis are 
shown in table 5. According to table 5, 
the section intake (A) contributes 
5 pet to the total source contribution 



100 pet of the time; the stage loader- 
conveyor (B-A) , operating 100 pet of the 
time, contributes 58 pet to the total; 
roof support movement (D-B), operating 
56 pet of the time, contributes 30 pet 
to the total; the head-to-tail 
shearer cut (E-D), operating 56 pet of 
the time, contributes pet to the 
total; and the tail-to-head shearer 
cleanup (C-B), operating 44 pet of 
the time, contributes 7 pet to the 
total. 



TABLE 5. - Dust source data for Mine 5 



Samn line loration^... .......... 


A 


B (cleanup) 


C (cleanup) 


D (cut) 


E (cut) 




Samnl i np t ime .......•..>. .mi n. . 


41 
0.3 


18 
3.6 


18 
4.5 


23 
6.6 


23 


Dust concentration mg/m^.. 


6.4 


Dust source. ................... 


A 


B-A 


D-B 


E-D 


C-B 






Descriotion. ••.•••••••..•••••.. 


Section 
intake. 

0.3 
100 
0.3 

5 


Stage 
loader- 
conveyor. 

3.3 

100 

3.3 

58 


Support 
movement. 

3.0 

56 
1.7 

30 


Shearer 
(cut). 

20.0 

56 

0.0 




Shearer 


Dust source concentration 

mg/m3. . 
Time fraction of mining cycle 

pet. . 
Average source contribution 

mg/m3. . 
Percent of total source 
contribution 3 


(cleanup) . 

0.9 

44 

0.4 

7 



ISee figure 3. 

2Quantity (E-D) is actually negative: see Appendix C explanation. 

^Total source contribution, 5.7 mg/m^; this represents average exposure during cut- 
ting and not exposure for compliance purposes. 



This mine was regularly out of compli- 
ance. It is obvious that the two largest 
dust sources for this operation are the 
stage loader-conveyor (58 pet) and the 
roof support movement (30 pet). Refer- 
ring to table B-1, it can be seen that 
both stage loader-conveyor dust and roof 
support dust contributions fall outside 
the range for the longwalls in conqjli- 
ance. Note that the stage loader- 
conveyor dust is on the intake air side 
of the roof support movement and there- 
fore is a major contributor to the sup- 
port operator's as well as the shearer 
operator's exposure. 



The reason that the shearer operator 
exposure is so low is that the shearer 
was equipped with the Bureau-developed 
"shearer-clearer". 8 However, this device 
did not help the mine achieve con^jliance 
because the shearer was not the main 
source of dust, which can easily be seen 
from the data. 

^Kissell, F. N. , N. Jayaraman, C. Tay- 
lor, and R. Jankowski. Reducing Dust at 
Longwall Shearers by Confining the Dust 
Cloud to the Face. BuMines TPR 111, 
1981, 21 pp. 



11 



SUMMARY 



This report has shown: 

1. How to evaluate the dust sources on 
your double-drum shearer longwall opera- 
tion, regardless of cutting sequence, and 

2, How your results coii5)are with the 
cleanest double-drum shearer longwall 
operations. 

Since it is recognized that all opera- 
tions are different in some respect from 
each other, this paper has attempted 
to present enough examples to cover a 



variety of circumstances. Once the anal- 
ysis has been performed and the major 
dust source(s) identified, the effective- 
ness of any subsequent dust control tech- 
nique can be evaluated simply by repeat- 
ing the test program and con5)aring the 
results. The quantities to compare are 
the total source contributions in milli- 
grams per cubic meter before and after 
implementing a dust control technique. 
These quantities estimate the total 
shearer operator dust exposure during 
actual cutting of the coal. 



12 



APPENDIX A. —SAMPLING SEQUENCE 



As an example, a step-by-step sampling 
sequence is provided. It will be assumed 
for the example that a unidirectional 
head-to-tail cutting sequence (this sam- 
pling strategy will apply to all cutting 
sequences) is used and that the sampling 
locations are those as described in 
figure 3. 

1. A sampler package (stationary) is 
located at A to measure the section in- 
take dust concentration. It is turned on 
just prior to testing. 

2. One individual stands 15 to 20 
ft on the intake air side (D) of the 
shearer, and the other stands at the 
shearer midpoint (E), between the 
operators. They will collect mobile 
samples. 

3. Once the shearer has fully sumped 
into the face and cleared the headgate, 
the sampling pumps are turned on (note 
sampler start time). 

4. Before the shearer reaches the 
tailgate, the sampling pumps are turned 
off (note sampler stop time). 

5. This set of filters (set I) is 
changed and replaced with a different set 
(set 2). 

6. The survey team assume their same 
positions (B, C) for the tail-to-head 
cleanup pass. 

7. Once the shearer has begun the 
tail-to-head cleanup and has cleared 
the tailgate, the sampling pumps (set 
No. 2) are turned on (note sampler start 
t ime ) . 

8. Before the shearer reaches the 
headgate, the sampling pumps are turned 
off (note the sampler stop time). This 
sequence can be repeated over and over 
again by simply using filter set 1 and 
the head-to-tail pass and filter set 2 on 
the tail-to-head pass. 

9. When testing is finished, sampler 
package A is turned off. 

Some general instructions and comments 
concerning sampling should be made. 



a. The mobile samplers (B, C, D, and 
E) should not be turned on until the 
shearer is fully sumped into the face. 

b. The mobile samplers (B, C, D, and 
E) should be turned off just before the 
shearer completes the pass. 

The important point to be made in 
items 1 and 2 above is that the sampling 
should not include phases that are short 
pieces of the cutting sequence; that is, 
breaking out into the headgage or tail- 
gate, or wedge cutting at the snake. 
There may be minor contributions to the 
total dust exposure of the shearer oper- 
ator, and inclusion would conqjlicate the 
analysis. 

c. All sampler filters (except sam- 
pler A) must be changed after the sam- 
plers are turned off at the end of each 
pass. These will be used jver again for 
each successive and -IdenbiQai pass. Fil- 
ter changes can be performed in two ways. 
First, the filters themselves can be 
changed. Second, duplicate sampling 
packages (or vests) can be used and 
switched after each pass. 

d. All start-stop times of the sam- 
plers (including sampler A) must be re- 
corded. One convenient method of record- 
ing times is to use a small, permissible, 
minicassette voice recorder. 

e. It is necessary that a minimum of 
0.2 mg of dust be deposited on each fil- 
ter to provide accurate weighing of the 
filters (see appendix C). 



f . Two days 
recommended. 



of sampling are 



g. Sampler package A must be located 
in the primary intake airway (last open 
crosscut). Since its function is only to 
provide an estimate of the dust entering 
the section during the testing, package 
A can be left turned on during the entire 
testing program. 

h. The survey team members follow the 
shearer, maintaining their positions with 
respect to the shearer (B and C on the 
tail-to-head pass, D and E on the head- 
to-tail pass). See figure 3. 



13 



APPENDIX B. —SHEARER OPERATOR DUST SOURCE CONTRIBUTIONS 
FOR SHEARERS IN COMPLIANCE 



After dust source contributions are 
determined, it is important to know how 
each source con5)ares with longwall 
double-drum shearers that are regularly 
in coii?)liance. 1 Table B-1 presents two 
quantities for each major dust source: 
(1) the range of dust concentrations, 
and (2) the percentage range of each 
dust source's contribution for the six 



longwalls in a recent Bureau survey of 
longwalls regularly in con5)liance. It is 
important to emphasize that the dust con- 
centrations in table B-1 for the dust 
sources are those only during the actual 
cutting and cleanup operations and not an 
8-hr time -weigh ted average. As such, 
they can in no way be used for conpliance 
purposes. 



TABLE B-1, - Typical longwall ^ double-drum shearer dust source contributions 
obtained from a survey of six longwalls regularly in conqjliance 



Dust source 



Range of average source 

contributions during 
cutting, mg/m^ 



Range, pet of total 
contribution 



Section intake , 

Stage loader-conveyor: 

Cu tting ,( 

Cleanup 

Support movement , 

Shearer: 

Head-to-tail cut..,,, 
Tail-to-head cut.,.., 
Head-to-tail cleanup. 
Tail-to-head cleanup. 



20,2-0,83 

,3- ,8 
.1-1,0 
,0- ,3 

,1-2,0 
,9-2,5 
.2-2,5 
,7-1,0 



9-18 

7-19 
5-20 
0- 7 

4-45 
20-63 

5-54 
16-45 



^The values in table B-1 were obtained from longwalls in which the airflow was from 
headgate to tailgate, 

2lf an MRE equivalent is desired, multiply all concentrations throughout this paper 
by 1,38. This is unnecessary for the work proposed, however. 

30ne longwall was in con^jliance with a section intake of 1.4 mg/m^. This value was 
omitted because it is not believed to be representative of longwalls in coii5)liance. 



^Taylor, C. D., and R. A. Jankowski. How the Six Cleanest U.S. Longwalls Stay in 
Compliance. Pres. at the First Mine Ventilation Symp. , Tuscaloosa, Ala., Univ. Ala- 
bama, Mar. 29-31, 1982; Min. Cong. J., v. 58, No. 5, May 1982, pp. 37-40. 



14 



APPENDIX C. --FILTER WEIGHTS AND ERROR CONSIDERATIONS 



It was stated in appendix A, part e, 
that it is necessary that a minimum of 
0.2 mg of dust be deposited on each fil- 
ter to provide accurate weighing of the 
filters. There are two reasons for this. 
First, the standard preweighed filter 
cassettes are preweighed to only one dec- 
imal place, and low dust weights may pro- 
duce unreasonable weighing errors. Sec- 
ond, the balances used by mine operators 
may not be capable of accurately weighing 
filters with less than 0.2 mg of dust. 
Generally, obtaining 0.2 mg or more of 
dust can be accon5)lished by using the 
same filters over and over again so that 
each filter represents four passes or 
more. 

The use of a more accurate balance will 
allow the mine operator to collect less 
dust on the filters. 

It is important to state that the data 
presented in this paper were based on 
dust masses less than 0.2 mg. Although 
the filter cassettes used were preweighed 
to the nearest tenth of a milligram, they 
were reweighed before and after use to 
the nearest thousandth of a milligram. 

If the operator wishes to collect less 
than 0.2 mg of dust, as the Bureau did, 
high accuracy balances are available from 



MSHA. The Code of Federal Regulations 
(30 CFR, Part 70.209 D) permits mine 
operators to collect samples for test 
purposes, and the mine operators can 
request MSHA to preweigh and postweigh 
the filters to the desired precision, 
thus reducing the amount of dust neces- 
sary for accurate filter weights. 

Considering the generally small amounts 
of dust collected on each filter that can 
produce significant weighing errors, it 
is recommended that sampling pumps of the 
flow-regulating type be used, although 
non-flow-regulating pumps are acceptable. 
The former type of pump is recommended so 
that sampling error due to pump airflow 
variations is minimized. 

In the sampling analysis examples pre- 
sented, certain dust source contributions 
(for example, E-D) are listed as 
0.0 mg/m3, although the calculated value 
was slightly negative. This result can 
be attributed to sampling errors such as 
pump variation and weighing errors. How- 
ever, the important result is that the 
dust source was not a major contributor 
to the shearer operator's exposure. If 
it had been, the calculated quantity 
would have been positive, regardless of 
sampling error. 






INT.-BU.OF MIN ES,PGH.,P A. 26341 












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